Paper tube concrete form



June 3, 1958 B. D. cLARKsoN PAPER TUBE CONCRETE FORM Filed 001'.. 12, 1955 PRIOR APT INVENTOR.

@LANDING D. CLARKSGN ATTOPNE YJ' United States Patent() PAPER TUBE CONCRETE FORM Blanding D. Clarkson, Hartsville, S. C., assiguor to Sonoro Products Company, a corporation of South Carolina Application (lctober 12, 1955, Serial No. 540,116

2 Claims. (Cl. 25--118) This invention relates to paper tube forms for use in molding concrete columns and the like, and more particularly to an improved paper tube structure for such forms.

U. S. Patent No. 2,677,165, granted May 4, 1954, discloses a multi-ply, spirally wound, paper tube having the innermost ply thereof coated or lined with apolyethylene iilrn for resisting the abrasive action of concrete during pouring, and for covering all protruding fibers of the. inner ply to prevent the embedding of theseiibers in conf,

crete during setting or curing thereof, so as to facilitate subsequent stripping of the paper tube and adapt it to particular advantage as a concrete form.

According to the present invention, the advantages of a paper tube concrete form as disclosed in the above noted prior patent are improved still -further by arranging the structure of the paper tube so that the innermost plyor plies thereof will absorb moisture initially from the poured concrete in a uniform to effect a swelling of the paper tube structure and slight shifting thereof during the initial setting of the concrete, by which swelling and shifting subsequent adhesion of the paper tube to the concrete after setting is eliminated.

This improved result is obtained in accordance with the present invention by perforating the liner coating for the innermost ply of the paper tube uniformly with fine, closely spaced, perforations small enough to' prevent release of any of the inner ply protruding iibers from the covering aiforded by the liner coating but large enough to allow uniform transfer therethrough of moisture from the concrete to the paper tube structure. The perforations provided for this purpose are in the nature of pinholes spaced in the order of from about 1%6 to 1A inch apart, and may be formed in the course of manufacture or after the paper tube structure is fully formed, as desired.

A further feature of the present invention is the arrangement in the paper tube structure of an outer ply, with respect to the innermost coated ply, that is made waterproof so as to serve both as a barrier against penetration of moisture outwardly beyond this outer ply that might result in undue weakening of the paper tube structure, and as a means for retaining and concentrating the' absorbed moisture within the inner most plies and thereby insuring a uniform moisture distribution and consequent swelling eifect throughout these innermost plies adjacent the concrete Ibeing formed.

These and other features of the present invention are described in further detail below in connection with the accompanying drawings, in which:

Fig. l is a perspective view of a paper tube concrete form embodying the present invention;

Fig. 2 is an enlarged, fragmentary, sectional detail illustrating diagrammatically a paper tube structure arranged according to the present invention for use in a concrete form as shown in Fig. l; and

Fig. 3 is a generally corresponding sectional detail next applied as illustrated at 22, this ply 22 being wound- 2,836,874 Patented June 3, 1958 illustrating a difference in the forming action of prior art paper tube concrete forms.

Referring now in detail to the drawings, and more particularly at first to Figs. l and 2, the concrete form of the present invention comprises a paper tube formed by spirally winding a plurality of paper strips to form a laminated or multi-ply tubular body 10 of the required length and wall thickness, the spirally wound paper stripsv being bonded by a suitable adhesive interposed between them as they are wound and the wall thickness being proportioned for adequate form strength.

As indicated in Figs. 1 and 2, and as mentioned above, the innermost ply i2 of the paper tube 10 is characterized lby a liner coating 14 having a pattern of fine perforations 16 formed therein. This inner ply 12 may be coated in the manner disclosed in the above noted prior patent,

and the perforations 16 may usually be formed most conveniently and effectively in the coating 14 directly after it has been applied to the inner ply 12 in advance of the spiral winding operation. Y

In the spiral wound structure of the completed paper tube 10 (as shown best in Fig. 2),-the innermost ply 12 is disposed with the liner coating 14 at the inner face thereof, and is Wound with a butt joint. adjacent plies (as illustrated at 18 and 20) are then superimposed by spiral winding with butt joints in staggered relation to form, with the inner ply 12, the structural portion of the paper tube 10 in which moisture is j.

absorbed through the liner Vcoating perforations 16.

The previously mentioned waterproof barrier ply is with an overlapping joint so as to seal it against outward penetration of moisture therethrough. An advantageous form for this barrier ply 22 is a composite arrangement of two paper strips with an asphalt base binder interposed therebetween `by which the paper strips are secured together and the whole is rendered waterproof. Outwardly of this waterproof ply 22, such further plies (as 24 and 26) are added as needed to complete the required wall thickness, all additional intermediate plies 24 being wound with butt joints and the final exterior ply 26 being preferably applied with an overlapping joint lfor covering the outer surface to the best advantage. The relative position of the waterproof barrier ply 22 may `be shifted in the structure of the paper tube l0 as desired in dealing with particular circumstances, although it has been found in actual use that consistently good results are obtained when the waterproof ply 22 is arranged as the fourth ply from the inside.

It should also be noted that in arranging the inner coated ply 12, the purpose of using a butt joint is to avoid troublesome disadvantages that result from using an overlapping joint at the inner ply 12, both in stripping the paper tube form from the concrete and in iinishing the surface of the formed concrete. An overlapping inner ply joint has a marked tendency to embed in the concrete during forming so as to render subsequent stripping of the form diii'lcult, and further results in impressing a spiral groove corresponding to the Width of the overlapping joint in the surface of the concrete that is difcult to remove without a great deal of surface finishing. For these reasons, a butt joint has heretofore been considered preferable in paper tube concrete forms.

However, it is not possible, as a practical matter, to form a butt joint in spiral Wound construction of this sort that does not have some spacing between the adjacent edges at the joint. This spacing at the butt joint naturally results in forming a spiral ridge on the concrete surface which, taken alone, is not too objectionablebecause it can be removed rather easily; but in actual practice a simple ridge does not result at this spacing because One or more the butt joint cannot be 'maintained watertight, at least not uniformly. Accordingly, moisture tends to penetrate Y the butt joint from the concrete during forming and Wet the adjacent structure of the paper tube 'back of the innerl ply, causing 'it tofs'well solas tor-undercut thel surface of the concrete adjacent the ridge resulting at fthe butt joint.` This isY illustrated inFig.

g, inwvhich concrete is represented at C' being formed by a' prior art paper tube form 10' having an inner ply butt VVjoint' thereinY (not shown) resulting in a surface ridge r in theconcrete that has been undercut at each side by lswelling of the aclja cent paper tube structure, so that removal of the ridge rf will require finishing of the entire concrete surface.

In Fig.- 3, the comparable Aforming action YofY the paper tube form of the present invention isvshown as resulting in a simple ridge r on the surface of the concrete C being formed, Ythis different result being provided by theperforated liner ceating-Y on the inner ply i2 that ,allowsV uniform Ywetting and swelling of the entire, inner paper tube structure,rrather than just a portionthereof adjacent Vtheinn'er ply butt joint, and thereby ,leavesV only a simple ridge -on the vsurface of the concrete C toberern'oved in iinishing.

The, present invention has been described .in detail above forrpurposes cf Yillustration only and is'nOt n- 1 tendedV to be limited by this' description or otherwise except asrdetined in the appended claims. j I claim:

1. AY form for molding circular concrete columns and 30 the like, said Yform comprising a Vmulti-ply, spirally Wound,` circular paper tube of sufficient strength Vand Vrigidity to support a column of concrete poured therein,

the innermost ply of saidpaper tube being spirally wound with a butt joint and having a linericoating applied thereon that is resistant to the abrasive action of the concrete during pouring and`that covers all protruding bers of said ply so as to prevent the embedding of said bers in the poured concrete during setting, said liner coating being perforated uniformly withline, closelyV spaced, perforations small enough to prevent release of any of said protruding innermost ply bers `from the covering aiorded by said coating, but large enough to allow transfer therethrough of'moisture initially fromthe poured concrete lfor obtaining Va swelling in the structure of said paper tube during the initial setting of the concrete by which Ysubsequent adhesionY of said paper tube to the concrete after setting is eliminated, and an intermedi- Y. ate ply ofrsaid paper tube being spirally wound with any molding circular concrete columns and'the'like, tliejim#Y y provement which comprisesa coating for said innermost ply that is perforated uniformly with tine, closely spaced,

perforations 4small enough to preventV release of any' of.Y the protrudingV ply bers but1large enough to allowthe absorptionof moisture from the poured concr`ete,'a1'1clY an intermediate Vply spirally woundlwith anoVerIa'p'ped Waterproofed joint t0 Serve as a' barrieragainst penetra? i tion of moisture outwardly therefrom. Y Y' Y References Cited in thetile of this patent Y UNITED VS'IA'IESV PATENTS 1,954,788 Chambliss et a1. Ap.\17`,"19'34 2,296,553 Heritage et a1. sept. 22,1942

2,677,165 Copenhaver et al May 4, 1954 

